i just got a xl2420XT today... i've never said "oh my god..." more times opening and using a new peice of hardware before.
I came from a 21.5 non-LED backlit LCD monitor (60hz)... and i was blown away.
the monitor is beautiful, very thin bezel (the menu is a billion times easier, they're non-dedicated touch buttons, if that makes any sense). the stand is something i felt like i should have paid a lot for separately, it adjusts height, pitch, tilt, rotation extremely easily..
I don't have the other monitor you're looking at, but all i can do is vouch for the excellence of the xl2420. and right now you can get it off benq.com for pretty cheap, especially if you find the 10% coupon floating around the forums here.